<template>
    <div class="music-list">
        <div class="back" @click="goBack">
            <i class="icon-back"></i>
        </div>
        <h1 class="title">{{title}}</h1>
        <div class="bg-image" ref="bgImage" :style="bgImageStyle">
            <div class="play-btn-wrapper" :style="playBtnStyle">
                <div v-show="songs.length > 0" @click="random" class="play-btn">
                    <i class="icon-play"></i>
                    <span class="text">随机播放</span>
                </div>
            </div>
            <div class="filter" :style="fliterStyle"></div>
        </div>
        <scroll v-no-result:[noResultText]="noResult" v-loading="loading" :probeType="3" @scroll="onScroll" :style="scrollStyle" class="list">
            <div class="song-list-wrapper">
                <song-list @select="selectItem" :songs="songs"></song-list>
            </div>
        </scroll>
    </div>
</template>

<script>
import Scroll from '@/components/base/scroll/scroll'
import SongList from '@/components/base/song-list/song-list'
import { mapActions } from 'vuex'
    const RESERVED_HEIGHT = 40
    export default {
        name: 'music-list',
        props: {
            songs: {
                type: Array,
                default() {
                    return []
                }
            },
            title: String,
            pic: String,
            loading: Boolean,
            noResultText: {
                type: String,
                default: '抱歉，没有找到可播放歌曲'
            }
        },
        data() {
            return {
                imageHeight: 0,
                scrollY: 0,
                maxTranslateY: 0
            }
        },
        components: {
            Scroll,
            SongList
        },
        computed: {
            noResult() {
                return !this.loading && !this.songs.length
            },
            playBtnStyle() {
                let display = ''
                if (this.scrollY >= this.maxTranslateY) {
                    display = 'none'
                }
                return {display}
            },
            bgImageStyle() {
                const scrollY = this.scrollY
                let zIndex = 0
                let paddingTop = '70%'
                let height = 0
                // iphone兼容
                let translateZ = 0
                if (scrollY > this.maxTranslateY) {
                    zIndex = 10
                    paddingTop = 0
                    height = `${RESERVED_HEIGHT}px`
                    translateZ = 1
                }
                let scale = 1
                if (scrollY < 0) {
                    scale = 1 + Math.abs(scrollY / this.imageHeight)
                }

                return {
                    zIndex,
                    paddingTop,
                    height,
                    backgroundImage: `url(${this.pic})`,
                    transform: `scale(${scale})translateZ(${translateZ}px)`
                }
            },
            fliterStyle() {
                let blur = 0
                const scrollY = this.scrollY
                const imageHeight = this.imageHeight
                if (scrollY >= 0) {
                    blur = Math.min(this.maxTranslateY / imageHeight, scrollY / imageHeight) * 20
                }
                return {
                    backdropFilter: `blur(${blur}px)`
                }
            },
            scrollStyle() {
                return {
                    top: `${this.imageHeight}px`
                }
            }
        },
        mounted() {
            this.imageHeight = this.$refs.bgImage.clientHeight
            this.maxTranslateY = this.imageHeight - RESERVED_HEIGHT
        },
        methods: {
            goBack() {
                this.$router.back()
            },
            onScroll(pos) {
                this.scrollY = -pos.y
            },
            random() {
                this.randomPlay(this.songs)
            },
            selectItem({song, index}) {
                this.selectPlay({
                    list: this.songs,
                    index
                })
            },
            ...mapActions([
                'selectPlay',
                'randomPlay'
            ])
        }
    }
</script>

<style lang="scss" scoped>
  .music-list {
    position: relative;
    height: 100%;
    .back {
      position: absolute;
      top: 0;
      left: 6px;
      z-index: 20;
      transform: translateZ(2px);
      .icon-back {
        display: block;
        padding: 10px;
        font-size: $font-size-large-x;
        color: $color-theme;
      }
    }
    .title {
      position: absolute;
      top: 0;
      left: 10%;
      width: 80%;
      z-index: 20;
      transform: translateZ(2px);
      @include no-wrap();
      text-align: center;
      line-height: 40px;
      font-size: $font-size-large;
      color: $color-text;
    }
    .bg-image {
      position: relative;
      width: 100%;
      transform-origin: top;
      background-size: cover;
      .play-btn-wrapper {
        position: absolute;
        bottom: 20px;
        z-index: 10;
        width: 100%;
        .play-btn {
          box-sizing: border-box;
          width: 135px;
          padding: 7px 0;
          margin: 0 auto;
          text-align: center;
          border: 1px solid $color-theme;
          color: $color-theme;
          border-radius: 100px;
          font-size: 0;
        }
        .icon-play {
          display: inline-block;
          vertical-align: middle;
          margin-right: 6px;
          font-size: $font-size-medium-x;
        }
        .text {
          display: inline-block;
          vertical-align: middle;
          font-size: $font-size-small;
        }
      }
      .filter {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: rgba(7, 17, 27, 0.4);
      }
    }
    .list {
      position: absolute;
      bottom: 0;
      width: 100%;
      z-index: 0;
      .song-list-wrapper {
        padding: 20px 30px;
        background: $color-background;
      }
    }
  }
</style>
